Tar Paper is an Issue! Upon buying a house 7 years old I found the roof to have no tar paper, the reason I found out is the shingles blew off in a storm and the roof leaked and caused water damage in the ceilings. I have Steeper pitched roofs and The Tar Paper DOES prevent rain from Gettin in. I called the building inspecter and found there is a building code forcing builders to use tar paper!